DESCRIPTION: (Applicant's Abstract) The cytokine interleukin-10 (IL-10) has shown therapeutic potential in a preclinical model of breast cancer. IL-10 is well tolerated in human volunteers. Expression of IL-10 as a transgene is associated with immune activation. For example, IL-10-engineered tumor cells immunize mice against challenge with the parent tumor and lead to enhanced generation of nitric oxide, elevated natural killer activity and induction of cell death. For each activity, the actions of IL-10 were indirect and dependent on the presence of interferon-gamma (IFN-gamma). IL-10 expression also results in the induction of the IFN-gamma-regulated genes Mig-1 and Gbp-1/Mag-1. Mig-1 protein has antitumor activity against human lymphomas. This application will test the hypothesis that IFN-gamma, mig-1 and/or gbp-1 expression are critical to the expression of antitumor activity by IL-10. Specific Aim 1 will determine the role of IFN-gamma in IL-10 mediated tumor inhibition. Using IFN-gamma mutant mice as well as neutralizing IFN-gamma antibody, the contribution of IFN-gamma to tumor inhibition mediated by IL-10 will be determined. Specific Aim 2 will determine the role of mig-1 in the therapeutic response to IL-10. Several approaches including the use of mig-1 antisense and mig-1 overexpression will be used to evaluate the contribution of mig-1 to tumor inhibition. If antitumor activity is identified for mig-1, the mechanism of action will be determined. Specific Aim 3 will determine the role of gbp-1/mag-1 in the therapeutic response to IL-10. The effect of gbp-1 overexpression and gbp-1 antisense on IL-10 mediated tumor inhibition will be determined. Specific Aim 4 will examine the role of IL-10 in control of human breast cancer. The effect of IL-10 overexpression on the growth and metastasis of human breast cancer cells will be determined. The role of mig-1 and gbp-1 will be examined in human tumors.